Various mechanisms and methodology have been used in the past to remove gravel that is incorporated into flat asphalt type roofs. There are several reasons that gravel is incorporated into such roofs. It is often used as ballast to hold the roofing material down in windy conditions, particularly when "membrane" or unitary type roof coverings are used. It also serves to protect the roofing materials from the sun, hail and the like. In some applications it serves as a decorative coating. When a roof having such a gravel covering is to be removed or portions of it are to be repaired the old roofing must first be removed. Part of the removal process is the removal of the gravel which covers the old roof. The gravel that is used in such roofing applications varies in size, ranging from a size known in the industry as "pea gravel" up to gravel having a two inch diameter. When this gravel is of the pea gravel size it is most often removed by sweeping. This is accomplished using either hand operated brooms or sweeping machines which use a rotating, solid core brush to move the gravel into windrows where it is subsequently hand shoveled into wheelbarrows and the like. When the gravel is relatively coarse, having a diameter of one to one and a half inches, the solid core brush sweepers cannot effectively move the gravel into windrows. Most frequently such gravel is hand swept and hand shoveled into some sort of transport device such as a wheelbarrow or cart. Considerable labor, expense and time is expended in removing coarse roofing gravel by this means.
It has also been known to use a truck mounted suction device for the removal of coarse gravel to save labor and time. However, such devices are large and very expensive. They generally must be positioned on the ground alongside the building and consist of a large fan that provides suction to a flexible hose. The hose is mounted to a nozzle mechanism that is slowly moved across the roof to remove the gravel by suction to a gathering device mounted on the ground. Because of their size and expense, such devices are generally jobbed out and must be scheduled for each job. This often causes inefficiencies and lost time at job sites.
It has also been known in the past to attempt to remove coarse gravel using towed devices having large solid core brushes which were intended to "sweep" the gravel into an auger mechanism which subsequently moved the gravel to a drag chain that would convey the gravel away. However, such designs were found to be cumbersome because they were towed, they would not "sweep" well using a solid core brush, and frequently clogged in the drag chain and auger devices. A further disadvantage of such devices was the expense of the large solid core brush which had to be replaced periodically due to wear. As a result, such devices found little commercial success and today 99% of the coarse gravel removed from roofs is removed by hand shoveling the gravel into wheelbarrows and the like.